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@ -25,7 +25,7 @@ MongoDB automatically creates an `ObjectId()` if it's not provided.
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To create a database is sufficient to switch towards a non existing one with `use <database>` (implicit creation).
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The database is not actually created until a document is inserted.
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```sh
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```sh linenums="1"
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show dbs # list all databases
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use <database> # use a particular database
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show collections # list all collection for the current database
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@ -38,7 +38,7 @@ db.<collection>.insertOne({document}) # implicit collection creation
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## Operators (MQL Syntax)
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```json
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```json linenums="1"
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/* --- Update operators --- */
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{ "$inc": { "<key>": "<increment>", ... } } // Increment value
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{ "$set": { "<key>": "<value>", ... } } // Set value
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@ -79,7 +79,7 @@ db.<collection>.insertOne({document}) # implicit collection creation
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> **Note**: `$<key>` is used to access the value of the field dynamically
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```json
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```json linenums="1"
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{ "$expr": { "<expression>" } } // aggregation expression, variables, conditional expressions
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{ "$expr": { "$<comparison_operator>": [ "$<key>", "$<key>" ] } } // compare field values (operators use aggregation syntax)
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```
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@ -95,7 +95,7 @@ Insertion results:
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- error -> rollback
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- success -> entire documents gets saved
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```sh
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```sh linenums="1"
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# explicit collection creation, all options are optional
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db.createCollection( <name>,
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{
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@ -128,7 +128,7 @@ db.<collection>.insertMany([ { document }, { document } ] , { "ordered": false }
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### Querying
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```sh
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```sh linenums="1"
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db.<collection>.findOne() # find only one document
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db.<collection>.find(filter) # show selected documents
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db.<collection>.find().pretty() # show documents formatted
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@ -172,7 +172,7 @@ db.<collection>.find().hint( { $natural : -1 } ) # force the query to perform a
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[Update Operators](https://docs.mongodb.com/manual/reference/operator/update/ "Update Operators Documentation")
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```sh
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```sh linenums="1"
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db.<collection>.replaceOne(filter, update, options)
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db.<collection>.updateOne(filter, update, {upsert: true}) # modify document if existing, insert otherwise
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@ -181,7 +181,7 @@ db.<collection>.updateOne(filter, { "$push": { ... }, "$set": { ... }, { "$inc":
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### Deletion
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```sh
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```sh linenums="1"
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db.<collection>.deleteOne(filter, options)
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db.<collection>.deleteMany(filter, options)
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@ -199,7 +199,7 @@ Utility to import all docs into a specified collection.
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If the collection already exists `--drop` deletes it before reuploading it.
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**WARNING**: CSV separators must be commas (`,`)
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```sh
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```sh linenums="1"
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mongoimport <options> <connection-string> <file>
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--uri=<connectionString>
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@ -218,7 +218,7 @@ mongoimport <options> <connection-string> <file>
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Utility to export documents into a specified file.
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```sh
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```sh linenums="1"
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mongoexport --collection=<collection> <options> <connection-string>
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--uri=<connectionString>
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@ -272,7 +272,7 @@ Indexes _slow down writing operations_ since the index must be updated at every
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### Diagnosis and query planning
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```sh
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```sh linenums="1"
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db.<collection>.find({...}).explain() # explain won't accept other functions
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db.explain().<collection>.find({...}) # can accept other functions
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db.explain("executionStats").<collection>.find({...}) # more info
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@ -280,7 +280,7 @@ db.explain("executionStats").<collection>.find({...}) # more info
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### Index Creation
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```sh
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```sh linenums="1"
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db.<collection>.createIndex( <key and index type specification>, <options> )
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db.<collection>.createIndex( { "<key>": <type>, "<key>": <type>, ... } ) # normal, compound or multikey (field is array) index
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@ -302,7 +302,7 @@ db.<collection>.createIndex(
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### [Index Management](https://docs.mongodb.com/manual/tutorial/manage-indexes/)
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```sh
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```sh linenums="1"
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# view all db indexes
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db.getCollectionNames().forEach(function(collection) {
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indexes = db[collection].getIndexes();
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@ -339,7 +339,7 @@ handling connections, requests and persisting the data.
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### Basic Shell Helpers
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```sh
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```sh linenums="1"
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db.<method>() # database interaction
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db.<collection>.<method>() # collection interaction
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rs.<method>(); # replica set deployment and management
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@ -378,7 +378,7 @@ Log Verbosity Level:
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- `0`: Default Verbosity (Information)
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- `1 - 5`: Increases the verbosity up to Debug messages
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```sh
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```sh linenums="1"
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db.getLogComponents() # get components and their verbosity
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db.adminCommand({"getLog": "<scope>"}) # retrieve logs (getLog must be run on admin db -> adminCommand)
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db.setLogLevel(<level>, "<component>"); # set log level (output is OLD verbosity levels)
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@ -404,7 +404,7 @@ Events captured by the profiler:
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> **Note**: Logs are saved in the `system.profile` _capped_ collection.
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```sh
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```sh linenums="1"
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db.setProfilingLevel(n) # set profiler level
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db.setProfilingLevel(1, { slowms: <ms> })
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db.getProfilingStatus() # check profiler status
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@ -454,7 +454,7 @@ Built-in Roles Groups and Names:
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- Backup/Restore: `backup`, `restore`
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- Super User: `root`
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```sh
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```sh linenums="1"
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db.createUser(
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{
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user: "<username>",
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@ -509,7 +509,7 @@ Variable syntax in aggregations:
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Filters the documents to pass only the documents that match the specified condition(s) to the next pipeline stage.
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```sh
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```sh linenums="1"
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db.<collection>.aggregate([
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{ "$match": { "<query>" } },
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@ -541,7 +541,7 @@ Passes along the documents with the requested fields to the next stage in the pi
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- [`$sum`][$sum_docs]
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- [`$avg`][$avg_docs]
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```sh
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```sh linenums="1"
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db.<collection>.aggregate([
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{
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"$project": {
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@ -598,7 +598,7 @@ db.<collection>.aggregate([
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Adds new fields to documents (can be result of computation).
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`$addFields` outputs documents that contain _all existing fields_ from the input documents and newly added fields.
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```sh
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```sh linenums="1"
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db.<collection>.aggregate({
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{ $addFields: { <newField>: <expression>, ... } }
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})
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@ -610,7 +610,7 @@ db.<collection>.aggregate({
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The $`group` stage separates documents into groups according to a "group key". The output is one document for each unique group key.
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```sh
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```sh linenums="1"
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db.<collection>.aggregate([
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{
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"$group": {
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@ -629,7 +629,7 @@ db.<collection>.aggregate([
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Deconstructs an array field from the input documents to output a document for each element.
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Each output document is the input document with the value of the array field replaced by the element
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```sh
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```sh linenums="1"
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db.<collection>.aggregate([
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{ "$unwind": "<array-key>" }
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@ -647,7 +647,7 @@ db.<collection>.aggregate([
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### [`$count` Aggregation Stage][$count_docs]
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```sh
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```sh linenums="1"
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db.<collection>.aggregate([
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{ "$count": "<count-key>" }
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])
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@ -657,7 +657,7 @@ db.<collection>.aggregate([
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### [`$sort` Aggregation Stage][$sort_docs]
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```sh
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```sh linenums="1"
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db.<collection>.aggregate([
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{
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"$sort": {
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@ -676,7 +676,7 @@ db.<collection>.aggregate([
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### [`$skip` Aggregation Stage][$skip_docs]
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```sh
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```sh linenums="1"
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db.<collection>.aggregate([
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{ "$skip": "<positive 64-bit integer>" }
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])
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@ -686,7 +686,7 @@ db.<collection>.aggregate([
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### [`$limit` Aggregation Stage][$limit_docs]
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```sh
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```sh linenums="1"
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db.<collection>.aggregate([
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{ "$limit": "<positive 64-bit integer>" }
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])
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@ -701,7 +701,7 @@ The `$lookup` stage adds a new array field to each input document. The new array
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> **Note**: To combine elements from two different collections, use the [`$unionWith`][$unionWith_docs] pipeline stage.
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```sh
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```sh linenums="1"
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db.<collection>.aggregate([
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{
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"$lookup": {
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@ -724,7 +724,7 @@ Performs a recursive search on a collection, with options for restricting the se
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The collection on which the aggregation is performed and the `from` collection can be the same (in-collection search) or different (cross-collection search)
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```sh
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```sh linenums="1"
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db.<collection>.aggregate([
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{
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$graphLookup: {
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@ -754,7 +754,7 @@ Each output document contains two fields: an `_id` field containing the distinct
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The documents are sorted by count in descending order.
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```sh
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```sh linenums="1"
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db.<collection>.aggregate([
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{ $sortByCount: <expression> }
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])
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